Master of Science (MS)
Renewable Natural Resources
Recovery of heavy metals from chromated copper arsenate (CCA) treated southern pine wood samples with three different dimension was investigated by recovery with acetic acid, oxalic acid and phosphoric acid in microwave reactor. Diluted phosphoric acid mixed with acetic acid was found to be very effective to remove copper, chromium, and arsenic from spent CCA-treated southern pine sawdust at a high temperature and in a short time. No single acid can totally recover all these three metals in one step in this method. Oxalic acid was effective in removing chromium and arsenic, and acetic acid was effective in removing copper and arsenic; However, CCA cannot be recovered with the mixture of acetic acid and oxalic acid because of a possible conflict effect. The effects of mixed acid concentration, reaction time, and temperature in microwave on recovery of CCA-treated wood samples were determined. The minimal reaction condition for maximum extracting CCA elements was 2.75% phosphoric acid mixed with 0.5% acetic acid, for 10min. at 130°C. The total recovery rate of CCA can reach 100% arsenic, 93.5% chromium, and 98.5% copper in one step. Statistical analysis showed the concentration of phosphoric acid and temperatures were two important factors. Three sizes of wood chips were also extracted in the microwave reactor. For the particle size of 0.5×0.5×0.5cm, 93.5% arsenic, 64.5% chromium, and 95.89% copper was extracted by 3.5% phosphoric acid mixed with 0.5% oxalic acid after 50 min at 130°C. Although it needs a longer time to achieve the total CCA extraction, the microwave reactor assisted acid extraction method was more effective than previous approaches.
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Yu, Bin, "Rapid microwave-assisted acid extraction of chromate copper arsenate (CCA)-treated southern pine" (2010). LSU Master's Theses. 207.